1. Field of the Invention
The present invention relates to magnetostrictive displacement or distance measuring transducers, and more particularly to magnetostrictive transducers having modular construction including for displacement or distance measuring and adapted for easy configuration of assembly of field equipment after manufacture or assembly from stocked modules. This construction also facilitates modular construction of an explosion-proof field device.
2. Description of the Art
Magnetostrictive transducers having elongated waveguides that carry torsional strain waves induced in the waveguide when current pulses are applied along the waveguide through a magnetic field are well known in the art. A typical linear distance measuring device using a movable magnet that interacts with the waveguide when current pulses are provided along the waveguide is shown in U.S. Pat. No. 3,898,555.
Devices of the prior art of the sort shown in U.S. Pat. No. 3,898,555 also have the sensor element embedded into the protective housing which also houses the electronics to at least generate the pulse and provide certain mounting means associated with the device for the customer.
U.S. Pat. No. 5,313,160 teaches a modular design in which the sensor and electronic assembly can be removed from the application package. In the application package is the outer housing which is used by the customer for mounting an attachment of the sensor and electronics assembly with the end device whose position is to be measured. Sensor designs of the past have required delicate handling until the fabrication of the total unit, including the outer housing and electronics, has been completed. Prior art also utilizes difficult to produce and expensive methods to suspend the waveguide and to prevent the reflection of the desired sonic strain wave. Prior high performance waveguide suspension systems utilize thin elastomer spacer discs which are individually positioned along the entire length of the waveguide. Installation of the discs is a time consuming, usually manual, operation. The best performing damping devices in use utilize molded rubber elements with a central hole. These are difficult to mold and time consuming to apply.
The prior art has deficiencies in that the electronics are included within the waveguide suspension device and an expensive means for waveguide suspension is utilized. The prior art also has deficiencies by not having modular construction and pre-assembled sensor elements. Further if different sizes are needed, the unit must be removed. But in the prior art, the sensor and the electronic package were not removable and interchangeable because of the application electronics being attached.
It is an object of the present invention to provide for an easy configuration or assembly of field equipment after manufacture or assembly from stocked modules, including modular construction of an explosion proof sensor.
It is a further object of the present invention to remotely locate the sensor from the electronics.
The present invention relates to a modularly constructed magnetostrictive transducer of the sort set out in U.S. application Ser. No. 08/500,004 filed Jul. 10, 1995, having a modular constructed magnetostrictive transducer, permitting a pre-assembled sensor element. A sensor cartridge which may be used as an explosion proof probe and which is environmentally protected and mechanically strong for direct use in process control applications is disclosed. The outer housing can be made from any weldable metal, and a sheet of teflon or other plastic can be added, if needed for chemical resistance. The pre-assembled sensor elements allow easy configuration or assembly of field equipment after manufacture or assembly of the sensor element. It also permits potting for environmental seal and explosion proof construction. The transducer would be then a rugged component, and may be equipped with threading to thread to another explosion proof housing which contains the mating electronics. For explosion proof configurations, the explosion proof material is anchored within the housing to be held in place when exposed to higher pressures.